Staving Off an Ice Age

Staving Off an Ice Age

Global warming may not be all bad, and it may not be all that recent.

Drilling deep into the ice of Antarctica and Greenland, scientists have found a different story, including some thought-provoking surprises.1 They see hints of a providential connection between global warming and civilization’s development-not to mention survival.

As rings tell the story of a tree-not just its age but also conditions affecting its growth-so, too, the layers in Earth’s oldest and thickest ice packs reveal the history of Earth’s atmospheric and temperature conditions. Each layer traps some air bubbles as it is buried below the next, and these bubbles can be analyzed when scientists extract cylindrical “cores” from the ancient ice fields.

What has motivated detailed analysis of deep ice cores (one is three kilometers long!) is the desire to determine when the next ice age will begin. As it turns out, that ice age should have begun already. In fact, it would have begun several thousand years ago had it followed the warming-and-cooling pattern made clear by those cores (a pattern explained by familiar solar system cycles, including precession of the tilt in Earth’s rotational axis, variations in the inclination of Earth’s orbit, and variations in the ellipticity of Earth’s orbit).2 So, what kept-and still keeps-the ice at bay?

The deforestation of Eurasia to make way for intensive crop cultivation and pasture land about 6,000-8,000 years ago apparently raised the atmospheric carbon dioxide level from 245 parts per million to 285 parts per million. A few thousand years later, extensive irrigation (for rice farming, especially) and increased cattle breeding-yielding larger numbers of these large domestic animals and greater quantities of milk and meat per animal-raised the atmospheric methane level from 450 parts per billion to 700 parts per billion.3 Because carbon dioxide and methane efficiently trap the sun’s heat (that’s why they’re called “greenhouse gases”), Earth’s surface began to warm. It warmed enough, in fact, to forestall the onset of the ice age that Earth’s orbital pattern predicted, a pattern firmly established for hundreds of thousands of years, as attested by the ice core studies.

In the industrial/technological age, human activity has continued to increase atmospheric concentrations of greenhouse gases. The extent of that warming has raised some alarm, and it does threaten Earth with some potentially dangerous consequences if it is not managed wisely. However, it has also stretched the time window for relatively comfortable, civilization-essential climatic conditions.

Consider this series of “amazing coincidences” that worked-apart from human understanding or awareness-to benefit human survival and sustain civilization’s advance: Though humanity came on the scene 50,000 years ago or more (according to biblical genealogies, archeological discoveries, and DNA analysis), the massive deforestation program waited at least 40,000 years. It was initiated just when the cooling cycle would normally begin. Then, for some unknown reasons, humans switched from primary dependence on easy-to-domesticate goats and sheep to dependence on the more difficult-to-domesticate cows, further sustaining the warmth. Next humans launched an incredibly difficult farming enterprise-extensive irrigation for rice production.

All these changes seem to have occurred with just-right timing and amplitude. How is that possible? It seems reasonable to conclude that divine providence, rather than dumb luck, is on the side of humanity-past, present, and future.

  1. William F. Ruddiman, Stephen J. Vavrus, and John E. Kutzbach, “A Test of the Overdue-Glaciation Hypothesis,” Quaternary Science Reviews 34 (2005): 1-10.
  2. William F. Ruddiman, “How Did Humans First Alter Global Climate?” Scientific American (292:3), March 2005, 46-53.
  3. Ruddiman, Vavrus, and Kutzbach, 2.